1. Field of Invention
Exemplary aspects of present invention relate to surface-emitting type semiconductor lasers and methods for manufacturing the same.
2. Description of Related Art
A surface emitting semiconductor laser is a semiconductor laser which emits laser light in a direction perpendicular to a semiconductor substrate. Since surface emitting type semiconductor lasers have excellent characteristics including, for example, easy handling, low threshold currents, etc., compared to related art edge emitting semiconductor lasers, application of surface emitting type semiconductor lasers to a variety of sensors and light sources for optical communications are expected. However, the control of polarization planes of a surface-emitting type semiconductor laser is difficult because of the symmetry of its planar structure. Therefore, when a surface-emitting type semiconductor laser is used for an optical system with a polarization dependence, instability of polarization planes causes noise. In this respect, a variety of related art methods to control polarization planes are discussed below.
Japanese laid-open patent application HEI 5-67838 discloses a method to control polarization planes by providing a diffraction grating within a resonator. In this case, only specific polarization remains within the resonator, and only a mode having the polarization oscillates. However, its manufacturing method is complex and therefore stable manufacture may be difficult.
Japanese laid-open patent application HEI 6-53599 discloses a method to control polarization planes by forming quantum fine wires in an active layer. In this case, the quantum fine wire structure exhibits strong polarization characteristic because quantum confinement exists in its in-plane direction. However, its manufacturing method is complex, and therefore stable manufacture may be difficult.
Japanese laid-open patent application HEI 10-209566 discloses a method to control polarization planes by providing a control electrode. In this case, by injecting an electrical current into the control electrode, the oscillation mode and polarization of laser light can be controlled, and the beam profile can also be adjusted. However, according to this method, a power supply source for control is required, and the power consumption may increase.